Rolling mill

ABSTRACT

A rolling mill for attenuating elongated metal stock by the rolling method, wherein the rolls are rotated about axes substantially inclined to the direction of stock motion and are also rotated as a group about an axis through the center of the stock.

llited States atent 1191 Bretschneider 1 ay 29, 11973 1 ROLLING MILL [56] References Cited [75] Inventor: Erich Bretschneider, Buderich, Ger- UNITED STATES PATENTS many 2,363,476 11/1944 Bannlster ..72/364 [73] Assignee: Siemag Siegener Maschinenbau 252;; Gesellschafi beschrankt 3I014I519 12 1961 Wright :::72/78 Dahlbruch, Germany 3,415,090 12/1968 Kirpichnikov et a1. ..72/449 700,360 5/1902 McTear ..72/78 [22] Flled' 1970 1,990,607 2/1935 Kocks ..72 7s 3,363,442 1/1968 Kennedy et a1 ..72/78 [21] Appl. No.: 81,934

Primary Examiner-Richard J. Herbst Related US. Application Data Atmmey Nrman Blodgett [63] Continuation-impart of Ser. No 749,178, July 31, [57] ABSTRACT l968,abandoned.

A rolllng m1ll for attenuatmg elongated metal stock by [52] U S Cl 72/78 72/100 the rolling method, wherein the rolls are rotated about B21b 13/20 axes substantially inclined to the direction of stock motion and are also rotated as a group about an axis [58] Field of Search ..72/77, 78, 126, 100

through the center of the stock.

12 Claims, 4 Drawing Figures PATENTEL -#2 3.735.617

SHEET 1 OF 2 IN VENTOR. ERICH BRETSCHNIEDER BY 10P A ATTRNEY PATENTED 3,735,617

SHEET 2 OF 2 Wal "'0, 0

ROLLING MILL REFERENCE TO COPENDING APPLICATIONS BACKGROUND OF THE-INVENTION It is common practice in reducing metal stock of circular cross-section from a larger to a smaller diameter to use driven rolls which are slightly tapered in the direction of the rolling axis. The taper of the driven rolls is selected in sucha way that the material to be reduced may pass several times through the zone of deformation and so that an axial advance of the stock is guaranteed. In such rolling mills, it has proven to be of a disadvantage that tensile stresses are developed withinthecore of the rolled stock, because this leads to structural defects. Particularly, when the rolls are driven with their axes parallel to the axis of the stock, there is such a severe differential in relative speeds between the surface of the rollers and the surface of the stock being reduced that the outer layers of the stock are actually separated from the core. Furthermore, it has proven to be a disadvantage that the rolling stock rotates about an axis through its center during the rolling process and this causes twisting. Because of the latter twisting of the stock, it has been possible to use this method only for short lengths of stock. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a rolling mill using tapered rollers rotating about axes lying at substantial angles to the stock, wherein the stock is not subjected to a twisting action.

Another object of this invention is the provision of a rolling mill capable of producing a substantial reduction in cross-section in one roll pass.

A further object of the present invention is the provision of a rolling mill capable of producing a reduction in cross-sectional area of an elongated workpiece, which reduction is the equivalent of several of the reductions possible in conventional rolling mill stands.

' It is another object of the instant invention to provide a rolling mill of the tapered-roll type which is capable of rolling long lengths of stock.

A still further object of the invention is the provision of a rolling mill of the tapered-roll type, wherein extremely large reductions in cross-section can be produced without the production of internal stresses within the stock and in which roll wear is substantially reduced.

Another object of the invention is the provision of a rolling mill capable of producing substantial reduction of stock size without producing separation between the outer layers and the core.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, the present invention consists of a rolling mill for the reduction of elongated stock of circular cross-section, having a housing through which the stock passes in the direction of its length, having a roll support element mounted in the housing for rotation about a main axis extending lengthwise of the stock, and having a plurality of tapered rolls mounted in the support element symmetrically of the main axis, each roll being mounted for rotation about a secondary axis substantially inclined to the main axis, and having means for rotating the rolls and the support element to bring about an axial advance and a reduction of the stock without twisting it.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a somewhat schematic, vertical sectional view of a rolling mill embodying the principles of the present invention,

FIG. 2 is a sectional view of a portion of the invention,

FIG. 3 is a front elevational view taken on the line III- III of FIG. 1, and

FIG. 4 is a vertical sectional view taken on the line IV-IV of FIG. 1.

In FIG. 1 is shown schematically a rolling mill 10 in which is provided a drive roll 37 of frusto-conical or mushroom shape which is cantilevered, that is, carried at the end of a supported shaft, and has its axis of rotation lying at a substantial angle to a main axis AA of the stock. This means that the differences in the ratio of roll peripheral speed to stock peripheral speed which occur along the work zone 38 in the rolling mill 10 are relatively low. An additional working zone 39 for smoothing is added to the forming zone 38. This compact design is made possible by use of a roll support element, such as a planetary housing 16 on which a roll support element 41 is mounted. The planetary housing 16 is supported on a hollow shaft 11 carrying a sun gear 42. The sun gear engages a planetary gear 17 which, in turn, is engaged with an intermediate gear 44. The gear 44 is mounted on the drive shaft of a bevel gear 45 through which it is possible to achieve the desired inclination of the axis of a driven roll shaft 19 relative to the axis of the stock in the deformation area. The teeth of the bevel gear are formed in such a way that the slope relative to the main axis is made possible and, at the same time, the advance movement of the stock by means of the spiral movement of the driven rolls relative to the stock can take place. In this schematic illustration, some of the supplementary parts are not shown, since they are well known in the art. This arrangement of the three rolls provides for the centering of the stock and also for the formation of a higher core density in the stock. The main drive is brought about by a motor 12 engaging a rim gear 47. Also, a motor 14 of low output engages the hollow shaft 11 which carries the sun gear 42 so that, by a'suitable control means, any tendency to rotation of the stock may be completely eliminated. An adjusting device 48 provides for a selection of the position of the drive roll shafts through a thrust bearing 49, thus permitting the axial adjustment of'the roll along with the axis of its shaft 19. To insure the engagement of the bevel gear 45 and a spindle bevel gear 51 at all times, a spline shaft section is arranged on the roll axis shaft 19, so that the bevel gear 51 can be moved lengthwise thereof.

The use of an arrangement as shown with a steep angle of the drive roll axis relative to the stock axis permits the use of a live roll which causes the reduction of the rolling stock in one zone and another further extended zone to smooth the stock and give it a fine working. At the same time, it is possible to achieve the same ratio of roll peripheral speed to the stock peripheral speed throughout the deformation zone. It is also possible, at the same time, to adjust the rolls with relatively small output and, therefore, make the determination of the final cross-section of the rolling stock.

The invention is not restricted to rolling stock of circular cross-section. The introduced stock bar may deviate from the circular cross-section and may have, for example, the shape of a polygon. The arrangement of three drive rolls on one roll carrier has proved to be successful in centering the rolling stock by this method and also in achieving the proper core density.

The above-described tapered rolling mill has the known advantage of such rolling mills, namely, the large reduction within one rolling mill stand with a moderate speed of advancement of the stock. By eliminating the turning of the stock, stock of any length may be used, so that, not only may large cross-sections be worked, but also the use of such a mill recommends itself to use with a continuous casting procedure. This is brought about without separation of the outer layers of the stock from the core.

It can be seen that is is possible with the present invention to achieve large cross-sectional reductions in a rolling mill by reason of the use of tapered rollers which are guided along the rolled stock surface in a curve of spiral form, so that each area of the surface passes between the rollers, and one achieves the action of a corresponding number of conventional rolling passes. At the same time, a simple method of advancing the stock is achieved.

FIG. 2 shows the details of the manner in which the roll 37 is mounted in the roll support element 41. The screw jack 48 is operative to adjust the roll shaft 19 axially to adjust the position of the deformation surface of the roll relative to the axis A-A of the stock 15. The axes of the three roll shafts intersect at a point P on the axis A-A and the generatrices of the frusto-conical surface of the roll 37 also intersect at that point. In the preferred embodiment, the surface 38 may be slightly curved outwardly, as shown in the drawings, rather than strictly conical to permit the axis of the roll shaft 19 to incline slightly to the plane of the drawing, as will be described more fully hereinafter.

FIG. 3 shows the manner in which the three rollers 37, 37', and 37" are grouped about the axis of the stock 15. As is evident in this view, the rolling mill built in accordance with the preferred embodiment is arranged with the axes of the roll shafts passing slightly to one side of the axis A-A and the point P. This is true, of course, of the intersections of the generatrices (vertices of the cones). That is why the surface of each of the rolls 37, 37', and 37" is approximately the frustrum ofa cone; as a practical matter, the slight outward bulge or curve is necessary because of the small angle of the roll shaft described above and the desired to maintain the ratio of roll surface speed to stock surface speed at a constant value along the entire length of the deformation zone.

FIGS. 1 and 4 show the details of the control means used for assuring against rotation of the stock 15. A contact wheel 53 engages the stock with a knife edge to reduce transmission of heat from the stock. The wheel is rotatably and resiliently mounted on a ring 55 which, in turn, is rotatably carrier on rolls. A gear segment on the outer periphery of the ring engages a gear mounted on the shaft of a potentiometer 54 having an internal resistance on which a slide is movable upon rotation of the potentiometer shaft. A source 56 of electrical power is connected to a center tap of the potentiometer and end taps are connected to the adjusting motor 14 to control the speed of the motor, so that the ring 55 and the wheel 53 stay in the center position, i.e., so that the stock 15 is not rotating. The main drive motor 12 is directly connected to the source 56.

As a practical matter, it is very difficult to maintain the effective roll diameter constant, and the same is true of the effective radius of the stock within the working zone 38. By using predetermined sizes of sun gear 42 and planetary gears 17, no twisting of the stock will be present, if these diameters remain constant. F urthermore, there is the difficulty of adjusting to every rolling condition and, therefore, to roll different effective diameters of stock. It is difficult to keep the diameter (that is, the shape of the surface of the driven rolls) at the optimum value during the rolling operation and also prevent the trend toward twisting of the stock only by driving the housing. Any twisting of the rolling stock, however, results in a twisting force on the ring 55 which results in an adjustment of the control system. Output signals from the control system 33 are carried to the motor 14. The motor may be at rest during an ideal transmission ratio, so that the drive of the driven rolls by the rotation of the planetary housing by means of the planetary gears 17 is transferred from the sun gear 42 in rest position. In the event that the control system registers a trend toward torsion of the stock, the motor 14 is activated and it introduces a slow turning of the sun gear 42 in that direction which reduces the trend of twisting. It, therefore, eliminates the torsion by a change in the rate of effective rotation of the driven rolls. In order to design the motors 14 for 3. corresponding lower output, despite the relatively high momentums encountered, the transmission is designed with a high reduction gear ratio.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

l. A rolling mill for the reduction of elongated solid stock, comprising:

a. a housing through which the stock passes along a line from a first point to a second point,

b. a roll support element mounted in the housing for rotation about a main axis coincident with the line,

c. three tapered rolls mounted in the support element symmetrically of the main axis, each roll being cantilevered and mounted for rotation about a secondary axis which intersects the solid stock, the rollers being mounted on a portion of the second axis which forms an acute angle with the first point on the line, and the rollers being cone shaped having a-vertex angle of greater than d. primary means for rotating the roll support element about the main axis,

e. intermediate means for transferring rotation of the roll support element about the main axis to rotation of the rollers about the secondary axis,

f. secondary means active on the intermediate means, for controlling the relative speed of rotation of the roll support element and the rollers, and

g. sensing means which is active on the secondary means to prevent rotation of the stock about the main axis.

2. A rolling mill as recited in claim 1, wherein the angle between the second axis and the tangent of a point on the work surface where the stock first contacts the work surface, is less than, that of a point on the surface that the stock last contacts.

3. A rolling mill as recited in claim 1, wherein the roll has a work surface which accepts the force of the reduction and transmits a resultant force vector which passes through the bearing.

4. A rolling mill as recited in claim 1, wherein the roll has a work surface a tangent of which forms an angle greater than 45 with the second axis.

5. A rolling mill as recited in claim 1, wherein planetary gears are mounted in the roll support element, a sun gear is mounted in the housing and engageable with the planetary gears to drive the rolls, and a motor is connected to the sun gear to supply a selected differential rate of reduction of the rolls and the roll support element.

6. A rolling mill as recited in claim 5, wherein the roll support element is driven by a second motor operating on a rim gear.

7. A rolling mill as recited in claim 6, wherein the second motor is provided with a high gear ratio and is controlled.

8. A rolling mill as recited in claim 4, wherein the planetary gears are connected to the roll by articulated spindles.

9. A rolling mill as recited in claim 4, wherein the planetary gears are connected to the rolls through a beveled gear drive.

10. A rolling mill as recited in claim 4, wherein the drive rolls are rotatably mounted in bearing chocks which are adjustable relative to the main axis.

11. A rolling mill as recited in claim 4, wherein the drive rolls are equipped with an adjusting device which determines the axial adjustment of the secondary axes of the drive rolls.

12. A rolling mill as recited in claim 4, wherein the drive rolls have a mushroom shape having a first deformation zone and a second smoothing zone. 

1. A rolling mill for the reduction of elongated solid stock, comprising: a. a housing through which the stock passes along a line from a first point to a second point, b. a roll support element mounted in the housing for rotation about a main axis coincident with the line, c. three tapered rolls mounted in the support element symmetrically of the main axis, each roll being cantilevered and mounted for rotation about a secondary axis which intersects the solid stock, the rollers being mounted on a portion of the second axis which forms an acute angle with the first point on the line, and the rollers being cone shaped having a vertex angle of greater than 90* , d. primary means for rotating the roll support element about the main axis, e. intermediate means for transferring rotation of the roll support element about the main axis to rotation of the rollers about the secondary axis, f. secondary means active on the intermediate means, for controlling the relative speed of rotation of the roll support element and the rollers, and g. sensing means which is active on the secondary means to prevent rotation of the stock about the main axis.
 2. A rolling mill as recited in claim 1, wherein the angle between the second axis and the tangent of a point on the work surface where the stock first contacts the work surface, is less than, that of a point on the surface that the stock last contacts.
 3. A rolling mill as recited in claim 1, wherein the roll has a work surface which accepts the force of the reduction and transmits a resultant force vector which passes through the bearing.
 4. A rolling mill as recited in claim 1, wherein the roll has a work surface a tangent of which forms an angle greater than 45* with the second axis.
 5. A rolling mill as recited in claim 1, wherein planetary gears are mounted in the roll support element, a sun gear is mounted in the housing and engageable with the planetary gears to drive the rolls, and a motor is connected to the sun gear to suPply a selected differential rate of reduction of the rolls and the roll support element.
 6. A rolling mill as recited in claim 5, wherein the roll support element is driven by a second motor operating on a rim gear.
 7. A rolling mill as recited in claim 6, wherein the second motor is provided with a high gear ratio and is controlled.
 8. A rolling mill as recited in claim 4, wherein the planetary gears are connected to the roll by articulated spindles.
 9. A rolling mill as recited in claim 4, wherein the planetary gears are connected to the rolls through a beveled gear drive.
 10. A rolling mill as recited in claim 4, wherein the drive rolls are rotatably mounted in bearing chocks which are adjustable relative to the main axis.
 11. A rolling mill as recited in claim 4, wherein the drive rolls are equipped with an adjusting device which determines the axial adjustment of the secondary axes of the drive rolls.
 12. A rolling mill as recited in claim 4, wherein the drive rolls have a mushroom shape having a first deformation zone and a second smoothing zone. 